Electric storage battery and process of manufacture



H. B. NlcHoLs 2,675,418

ELECTRIC STORAGE BATTERY AND PROCESS OF MANUFACTURE 4 Sheets-Sheet lApril 13, 1954 Filed March 21, 1952 April 13, 1954 H, B, NICHOLS2,675,418

ELECTRIC STORAGE BATTERY AND PROCESS OF' MANUFACTURE Filed March 21,1952 4 Sheets-Sheet 2 f! TTOR NE YJ April 13, 1954 H. B. NICHOLS2,675,418

ELECTRIC STORAGE BATTERY AND PROCESS OF MANUFACTURE Filed March 21, 19524-SheetsSheet 3 k 4 lNI/ENTOR.

#9v/ey i. /V/Mas /ITTORNEIJ pri 13, 1954 H. B. NICHOLS 2,675,418

ELECTRIC STORAGE BATTERY AND PROCESS OF MANUFACTURE Filed March 21, 19524 sheets-sheet 4 l0 2O 50 40 .50 60 T0 BY M ATTORNEYS Patented Apr. 13,1954 ELECTRIC STORAGE4 BATTERY PROCESS 0F MANUFACTURE Henry B. Nichols,Amherst, Mass.

Application March 21, 1952, Serial No. 277,757

(Cl. 13G-28) 9 Claims.

This invention relates to electric storage batteries and theirproduction, and more particularly, to alkaline storage batteries whichare known as nickel-cadmium storage batteries. It was long known thatfor best results such nickelcadmium batteries should operate with porouselectrode plates of sintered nickel powder particles having the poresloaded with the active materials for the positive and negativeelectrodes, respectively. However, in the past, the processes used informing sintered activated electrode plates for such nickel-cadmiumbatteries were unsatisfactory and the resulting plates varied widely intheir characteristics, and a great percentage of nickel-cadmiumbatteries produced with prior art sintered plates became defective inthe initial stage of their operation.

Among the objects of the invention are methods by which the sinteredelectrode plates for such nickel-cadmium batteries may be produced in away that makes it possible to obtain highly eective sintered electrodeplates for such batteries of consistent quality and characteristics on alarge scale production basis.v

Among the objects of the invention are also superior sintered electrodeplates for such batteries which eliminate the difficulties encounteredwith prior art electrode plates of this type.

It is also among the objects of the invention to provide nickel-cadmiumalkaline batteries having a novel electrode spacer which permits theconstruction oi compact batteries of this type having lower internalresistance and higher discharge capacity than prior batteries of thistype.

It is also among the objects of the invention disclosed herein toprovide a superior multicell ba tery assembly.

The foregoing and other objects of the invention will be best understoodfrom the following description of exemplifications thereof, referencebeing had to the accompanying drawings, wherein Fig. l. is a verticalsectional View, of an assembled battery cell made in accordance with theinvention;

l-A is a detail side view of the central portion of the top wall;

Fig. 2 is a cross-sectional view along line 2 2 of Fig. 1;

Fig. 3 is a top elevational view of the battery cell of Fig. 1; l

is a greatly enlarged cross-sectional view of a portion of a largesintered sheet formation representing the rst stage in form- 2 ingbattery electrode plates-of the invention with the plates shownexaggerated;

Fig. 5' is a plan View showing a portion ofA the same large sinteredsheet formation in a subsequent foi'ining stage;

Fig. 6 is a planV view similar to Fig. 5 of an individual batteryelectrode plate formed by cutting the sheet formation of Fig. 5;

Fig. 7 is a view similar to Fig. 6 of the vsame electrode plate in alater forming Stage with the electrode terminal tab ailixed thereto;

Fig. 8` is a cross-sectional view along line 8-8 of Fig. '7;

Fig. S-A is a view similar to Fig. 8 of a modified construction;

Fig. 9 is a plan view of a sub-'assembly of positive and negativeelect-rode plates and the interposed separator formations of suchbattery;

Fig. 10 is a cross-sectional view along line lillt of Fig. 9 with someof the parts shown xagger'ated for the sake of clarity;

Fig. 1l isv a cross-sectional view along line H--f-ll of Fig. 9', withsome of the parts shown exaggerated; and

Figs. ll-VA, ll-B and ll-C are curve diagrams giving typical operatingcharacteristics of a battery of the invention.

The principles underlying the features of the invention ydisclosedherein will be explained by reference to one practical form of a batterycell shown in Figs; l tor 3, and generally designated lil; The batterycell l0 comprises a flat casing having two extended sidewalls ll withadjoining two narrow side walls l2 and a bottom wall i3, the casingspace being enclosed at the top by a top Wall I5. The housing walls llto I5 are all made of a suitable alkali-resistant material. Suitableresin materials for this purpose are the nylons, polyethylene terephtate(Daeron), polyacrylonitrile, polystyrene, polyvinyl chloride and likesynthetic resins which arerresistant to alkali solutions.

Within the top wall l5 are mounted, and are held fixed and sealedtherethrough with a fluidtight seal, two metallic terminal members 2l ofopposite polarity providing terminal connections to the oppositepolarity battery plates of the electrode assembly generally designated.Ell held within the interior of the casing H. Each of the two terminalmembers 2l is made in the form ofl a metal shank, passing through anopening within the insulating top wall IS and having on its inner sidean enlarged head held seated across a sealing washer 23, of alkaliresistant rubber material, such as neoprene, against the overlyingseating surface of the top wall bordering the opening thereof. The shankhead 22 is held clamped to its seat by a sealing nut 24 threadedlyengaging the upper threaded portion of the terminal shank member 2i andclamped against the underlying seating surface of the top wall I8 toform a liquid-tight seal therewith.

The inner head 22 of each terminal member provided with downwardlyextending ear members 26 to which are affixed, as by welding, the upperends of a superposed opposite polarity array of strip-like electrodeleads or tabs 3l, 32 of the battery assembly 30. The two terminalmembers 2| are made of alkali-resistant metal, such as nickel.

The inner faces of the large side walls Il of the cell casing areprovided with short rib projections l l-i for holding the large sidesurfaces of the battery assembly 30 slightly spaced, such as by a gapspacing of about .020 to .O40 inch, from the inner walls of the casing.Similarly, the inwardly facing side of the bottom casing wall I3 isprovided at its opposite narrow end regions with the raised ledgeportions I3-I for holding the bottom edges of the electrode assembly 3Bat a small gap spacing, such as .020 to .040 inch, above the surface ofthe bottom wall i4.

The battery assembly 3l) is permeated by and held immersed within aliquid body of an electrolyte shown extending up to a level 4l which ishigher than the upper level of the electrode assembly 343. Theelectrolyte of such nickelcadmium batteries usually consists of a to 35%(by weight) solution of potassium hydroxide KOH in water. Excellentresults are obtained with a solution of potassium hydroxide as theelectrolyte.

The well known principles of operation of nickel-cadmium batterieshaving positive electrodes of nickelous hydroxide particles NMO-H); andnegative electrodes of cadmium hydroxide particles Cd OH 3 immersed inan electrolyte consisting of a solution of potassium hydroxide arebelieved at present to be substantially as follows:

When fully charged, the active positive electrode material consists ofnickelic hydroxide and the active negative electrode material consistsof cadmium. During the discharge, the active material of the positiveelectrode tends to reach a lower energy level involving a reduction ofits active nicirelic hydroxide material to the lower nickelous hydroxide2Ni(OH)2 and the releasing of negatively charged hydroxyl ions while thenegative electrode is oxidized to form cadmium hydroxide Cd(OH)2 and/orcadmium oxide and give up electrons to the external circuit. Inehargingwsuch cell, chemical changes take place at the positiveelectrode involving oxidation of its nickelous hydroxide material and/orthe release of oxygen while the active electrode material of thenegative electrode, to wit, the cadmium hydroxide and/or cadmium oxide,undergo a chemical change which involves the reduction of the cadmiumhydroxide and/or cadmium oxide4 to pure cadmium and the release ofhydrogen. Accordingly, gas will develop in the cell during the chargingprocess.

One phase of the present invention disclosed herein involves novelmethods and processes for the manufacture of sintered active electrodeplates for such nickel-cadmium battei which 4 will be now explained inconnection with Figs. 4 to 8.

In accordance with a phase of the invention, the electrode plates fornickel-cadmium batteries are formed by producing them out of largesintered sheet formation of nickel particles loaded and treated toembody in them the proper amount of the respective positive and negativeactive electrode material, the so-treated and formed large sheetformation being thereafter cut into properly formed electrode platesections of the required size out of which the electrode assembly of thebattery cell is formed.

In general, the process of forming the positive and negative electrodeplates out o large sheet formations in accordance with the invention,involves the following series of steps.

1st, a thin grid, reticulated sheet or a layer or gauze of metallicnickel is placed between two layers of fine nickel powder within asuitable Irefractory carrier or boat and sintered at an elevatedtemperature so as to form a self-supporting sheet formation of sinterednickel particles having embedded in its interior the thin backing gridor gauze of metallic nickel which provides electro-conductiveconnections and also strengthens and backs up the sheet formation.

2nd, the large sheet formation produced in the lst step is then placedin a die arranged to compact therein crosswise extending narrowseparation zones wherein the powder particles are compressed to veryhigh density, with the thickness of the zone substantially reduced tothe thickness of the metallic backing grid or gauze.

3rd, the large sheet formation of sintered. nickel powder having thincompacted subdivision zones is then further sintered or resintered at anelevated temperature in a protective atmosphere for increasing the bondbetween the metal particles resulting in sheet formations consisting ofsheet sections having to about 85% porosity separated by highlycompacted narrow separation zones of only 5 to 2% porosity or 95%r to98% density.

4th, depending on the size, one, two, or more processing tabs of nickelsheet material are welded to spaced portions along one edge of eachsheet formation which has been previously compacted to substantially thethickness of its backing screen or grid.

5th, an array of such large sheet formations is then loaded with thepotentially active material, to wit, a solution of nickel nitrate forthe pori.- tive electrode sheet formations and a solution of cadmiumnitrate for the negative electrode sheet formations.

6th, thereafter, the loaded arrays of sheets for the respectiveelectrodes are activated by placing them in a strong alkali solution ofeither sodium or potassium hydroxide subjecting them to a cathodicelectrolytic process whereby the nickel nitrate and cadmium nitratepreviously deposited or loaded into the pores is converted into thedesired active electrode material, to wit, nickel hydroxide and cadmiumhydroxide. for the positive and negative electrodes, respectively.

7th, the activated sheet formations are then washed to remove anynitrate deposited therein and also any loose particles deposited orpresent thereon.

8th, the washed sheet formations are then brushed or otherwise treatedwhile wet, as with a spray, to remove from their surfaces anyencrustatlons .of actirematencl nnd-,zanrgloocc partielesfprcsentthereon.

'Steps to 8 repeat-edili sequence a number ofl times'nntil all Sheetformations been properly icaded the active electrode materials.

9th, after drying, arrays of so-prepared sheet formations of alternatepolarity, with interposed separators, are then placed vin a forming bathand given a number oi .charging cycleseach followed `by a discharge.

10th, after-*properly ioading, activating and forming, the sheetformations are, after first Washing, thickness-sized while wet, as Vbycompacting in a sizing press to bring their active large areas to .thedesired thickness.

A11th, the sheet formations are then stacked fiat vand flattened under aWeight, and the weighed stack is dried.

12th, the large sheet formations are thereafter cutaiong the compactedthin separation zones and separated into sheet sections, each of thesize ofthe desired battery electrode plate.

13th, the edges of the electrode plate sections so formed by cutting thelarge 'sheet formations are then coated with cementitious material, forinstance, va plastic or synthetic resin coating material, to bind intoposition any particles which may have been loosened by the cuttingoperation and to cover any sharp edges of the backing screen formed or`exposed thereon as a result of the cutting operation.

14th, electrode llead tabs are then welded to compacted thin compactedcorner portions of the individual electrode plate sections, therebycompleting the individual electrode plates, whereupon they are ready forassembly into battery electrode sub-assemblies, lsuch as shown at 30 inFig. 1. Y

The individual steps'of the 'process' of the invention for forming theopposite polarity plate of a nickel-cadmium` battery inaccordance withthe invention in the manner outlined above will now be described inmoredetail.

In the 1st step, pure nickel powder is formed into a porous sinterednickel ypowder sheet formation. Fine nickel powder of -200 mesh preparedby heating nickel carbonyl at an elevated temperature within aprotective atmosphere, such as, cracked ammonia or puried hydrogen, is

suitable for'this purpose. It is also desirable to provide anelectrically highly conductive 'backing for the sintered nickel powdersheet formation. A reticulated grid-like thin sheet of nickel or a thinWire screen or gauze .of nickel wire is suitable as such backing. Suchreticulated or perforated nickel backingv sheet may also be formed by anelectro-deposition p:oc ess.v vVJhere wire gauze is used, its electricalconductivity maybe improved lby electro-depositing thereon in vbath athin stratum of nickel. Depending on the thickness of the finalelectrode plates, Ymetal sheets or wire mesh formed of wire havingsmaller or greater thickness may be used. 1 Thus, by way of example,very effective velectrode piates .025 inch thick, may beyproduced'with abacking sheet of nickel wire mesh of -wires'per inch'in'cross- Wisedirections, each wire having a thickness of .007 inch, such mesh beingconventionally designated 20 x 20 x .007 mesh. Similarly, very effectiveelectrode plates .050 inch-thick may be produced with-.a backingA sheetof nickel vire L6'xf16a1012..

' :By: @ways of v: example, z tor. producing slntered electrodeplate.-sheets of the inventionhaving 1 a --within a protectiveatmosphereof cracked arnmonia for 10 to 15 minutes until the nickel particles areiirmly sintered to each other and to the backing sheet and formtherewith a selfsupporting powder sheet formation of about .025 inch-thick with the sintered powder body exhibiting about 75 to 90%porosity. As the nickel powder layer shrinks in sintering, suitableallowance is made in dimensioning the 'powder layer deposited in themold prepartory to the sintering operation. Good results are obtainedwith sintering at 900 to 925'`C. 'for 12 to 10 minutes, yieldingsintered nickel powder sheet formew tions of about `82 to. `86%porosity.

Fig. i is a cross-sectional View of .a portion ci so-formed sinterednickel powder sheet formation 51 about .025 to .030 inch thickconsisting of sintered nickel powder particles in which is embedded anickel wire mesh gauze '53 Wherein the sintered nickel powder body has aporosity of 82 to 86% and is used for forming electrode plates of theinvention. The pores or interstices between the sintered nickel powderparticles are of microscopic dimensions.

In theZnd step, the sintered nickel sheet formation 5l is subjected tothe compacting treatment in which it is placed Within a compacting diefor forming along the large sheet formation 5l cross-wise extendingnarrow highly-compacted separation zones along which the sheet formationis subsequently cut into the separate electrode plate sections. Fig. 5is a plan view showing the general configuration of a sheet formation ofFig. 4 after it is given such compacting treatment. The compacted sheetformation 54 shown in Fig. 5 has cross-wise extending narrow separationzones 55 about le inch wide, and also narrow edge zones 5l, about g inchwide which are highly compacted to substantially the thickness of thescreen mesh 53 embedded therein. On the other hand, the major area ofeach section 5S bordered by the thin compacted zones 55 and 5l' is notcompacted so that it retains the desired porosity and may be formed intothe effective electrodes in the manner described hereinafter.

One of the compacted edge Zones, such as the upper edge zone 'l--s ofthe sheet formation (Fig. 5), is made somewhat wider, about 1/4 to 1/2inch and is used to provide processing connections thereto.

rThe compacting die is so shaped as to form at the corner of each platesection 553 a coi .pacted corner region 59 serving the electrodejunction of each electrode plate section d8. To simplify the compactingoperation, the coanpacting die is so designed as to form the compactedcorner terminal regions 5@ on four adjoining corners of four adjoiningelectrode sections of the sheet ior mation 54, as indicated Fig. 5'.Fig. shows in cross-section and exaggerated' for the sake clarity, thegeneral coniguration oi the main surface region of each electrode platesection and of the compacted separation zones or edge regions 55thereof. Depending on the requirements, 'such compacted terminal regionmay :performed .along another portion of the edge 'regions oftheindividual plate section eyof such sheet formation 54 (Fig. 5).

In the next 3rd step, the compacted sectionalized large sheet formation54 is subjected to an additional sintering treatment. In this additionalsintering treatment, an array of such large compacted sheet formationsis maintained at an elevated temperature within a similar oxidizingsupressing protective atmosphere for causing the particles of thesintered sheet to be very rmly and closely bound to each other. It hasbeen found desirable to effect the resintering treatment at a lowertemperature and for a shorter period than the original sintering, suchas about 650 to 950 C. for about '7 to 2 minutes. In producing platesabout .025 to .050 inch thick, good results are obtained by resinteringat about 870 C. for about 3 minutes.

Such resintering treatment is very effective in securing a tight bondbetween the wires of the Wire gauze 52 with the sintered nickel powderparticles along the thin compacted zones 55 and edges 57.

In the next 4th step, processing tabs 5i of nickel sheet material areattached, as by welding, to spaced portions of the somewhat widercompacted edge regions 57-i of each large sheet i formation 54 (Fig. 5)for use in the subsequent treatment steps.

In the next 5th step, the loading treatment, an array of similar sheetformations 55, such as shown in Fig. 5, are placed in a solution ofeither nickel nitrate or cadmium nitrate, for loading their porestherewith preparatory to the activating treatment in which they areformed either into positive or negative electrode plates, respectively.The porous sheet formation for the positive electrode is impregnatedwith a solution of nickel nitrate Ni(NO3)2.6H2O with a slight excess ofnitric acid. The porous sheet formation for the negative plates isimpregnated with a solution of cadmium nitrate Cd NO3 24H20. ableimpregnating solution of nickel nitrate is one which is nearly saturatedat room temperature of to 30 C. A suitable solution of cadmium nitrateis one which is similarly nearly saturated at such room temperature.Good results are obtained with a nickel nitrate solution having aspecific gravity of 1.6 and a cadmium nitrate solution having a specificgravity of 1.8 at room temperature. In this loading treatment, thesintered compacted porous sheet formations 54 are placed in a vessel,and after evacuation of the vessel, the nitrate solution is introducedinto the vessel for impregnating and loading the pores of the extendedelectrode area sections 58 of each sheet formation 5 with the propernitrate solution.

In the next 6th treatment step, the loaded sheet formations 54 for thepositive or negative electrode plates are activated by a cathodicelectrolytic process within a heated bath of an alkali solution ofeither sodium or potassium hydroxide for converting the nickel nitrateand cadmium nitrate loaded into the microscopic pores of the platesections into the desired active positive or negative electrodematerial, respectively. In the positive electrode plate sections of thesheet formation 54, the nickel nitrate loaded into its pores isconverted by the electrolysis into nickel hydroxide retained within thepores of the plate. In the negative electrode sections of the sheetformation 54 the cadmium nitrate loaded into its pores is converted bythe electrolysis into cadmium hydroxide, and some of vthe hydroxide isreduced into cadmium. The electrolizing bath may be formed of a 15 to25% solution of either A suitsodium or potassium hydroxide and. it iskept near the boiling point. By way of example, good results areobtained with a bath formed of a 20% solution of sodium hydroxidemaintained near its boiling point at about 100 to 110 C. For electrodeplates .025 to .050 inch in size, the electrolizing current may be about1/2 to 3 ampere per square inch of sheet formation, and it may belarger. Good results are obtained by treating such plates with anelectrolizing current of 2.5 ampere per square inch of sheet formation.

In the washing treatment, or step '7, each sheet formation which waselectrolyzed in the manner described above, is 'washed in ionized waterto remove any sodium or potassium nitrate formed or deposited in thepores or on the surface of the sheet formation; VCrood results areobtained by washing until the drip water from the washed sheet formationhas a pH of 7.0.

The washing treatment is followed with a brushing treatment of step 8for removing from the previously treated Ysheet formations surfaceencrustations formed by the loading and electrolysis treatments and anyloose particles loosened or otherwise present or formed on the sheetformations 54. To this end, the exterior of the washed sheet formationis brushed while wet with a brush having suitable bristles, such asnylon or polystyrene, dipped in ionized water. Alternatively, it may besprayed with a forceful spray of ionized water, and such spraying may becombined with the brushing. The washed and so brushed sheet formationsare then dried, for instance, air dried, in the air of an oven heated toC. or lower, until dry.

For effective results, it has been found essential to limit the durationof each electrolysis activation treatment to a relatively short time,and to subject each sheet formation to repeated sequences of loading,activating, washing, brushing and drying treatments until the properamount of active positive and negative electrode material has beendeposited in the microscopic crevices or pores of the sheet formations.

By way of example, in forming sintered electrode plates .025 to .050inch thick, good results are obtained by limiting each electrolysisactivation treatment to about 15 to 25 minutes, and repeating four tofive times similar sequences of loading, electrolysis-activating,washing, brushing and drying treatments for each sheet formation untilit shows the proper gain of active material by decreasing the originalporosity of 82 to 86% of the sintered powder body of the sheetformations to a porosity of about 45 to 65% or more specifically toabout 50 to 60%.

By way of example, in each electrolizing treatment of each repeatedtreatment sequence, good results are obtained with the electrolysiscarried on with a direct current utilizing a vessel of nickel as theanode for holding the sodium hydroxide solution constituting theelectrolytic bath and carrying on the electrolysis with a current whichat the startdevelops about one volt between the vessel and the sheetelectrodes immersed in the electrolyte. In each cycle, the electrolysisis carried on forabout 15 to 25 minutes until the voltage between thevessel and the immersed sheet formation increases to about 1.8 to 2volts.

By Way of example, for sheet formations having electrode plate sections41/2 inches square and .025 inch thick, each electrode section had aweight of about '72 grams before being subjected to the series ofloading and activating sequences of the type described above. Aftercompleting fourv se,-

quences of loading and activating treatments carried out in the mannerdescribed above,` the properly activated positive plate section showedaweight gain of 6.5 to 7 .5 grams, andea'ch properly activated negativeplate section'showed a Weight 5 gain of 11.5 to 14 grams. With thevoriginally sintered plates having aI porosity of 85 7), there peatedsequences of activating treatments reduce thus the porosity of theactivated plates to about 50 to 60% or give a weight gain of about 1.5to 1.7' grains per square inch for the positive plates and a weight gainof about 2.6 to 3.2 grams for-the negative plates.

In the next treatment step lil', thepropeilyfelectrolyzed and sizedsheet formations are subjected to series of electric charging anddischarging cycles, whereby they are properly-termed. Toth-is end,arrays of alternate positive Vand negative sheet formations are placedadjacentv to each other Within an electrolyte bath of a potassiumhydroxide solution with electrolyte pervioiusine sulating separatorsinterposedbetween adjacent opposite polarity sheet formations, whereuponthey are subjected to a series of electric charging and dischargingcycles. By way of example, with sheet formations .025 inch thick, goodresults are obtained if they are formed with the following series ofthree forming cycles: A

A first charging period of 30 hours at i045 ampere per square inchfollowed by a dischargeat .065 ampere per squar'einch until the voltageper cell drops to 1 volt; followed by A second charging period of hours'at .065 ampere per square inch followed by the same discharge as in thefirst cycle; followed by A, third and final chargingperiod of 7 hours.at the same rate as in the second cycle followe'd'by the same discharge.Y

The sintered nickel powder 'sheet formations produced by the 1stsinteringstep describedhere; inbefore, gives sintered powder particlesheetsY ofnickel varying in thickness by about'Y i510%. addition, theYseries of loading, activating and forming treatments, including therepeated load ing and electrolyzing sequences of thetyped'' scribedabove, results in' a growth. ofthe thickness of the treated sheetformations,

On the other hand, it is desirable thatbattey' electrode assemblies ofopposite polarity" having a required number of electrodeA plates, shouldbe generally of the same thickness. For thisfreason, it is importantthat the individual electrode plate sheets, at least each groupofelectro'del plates 0fthe same polarity, should likewise befof.substantially the same thickness.

In accordance with a phase of the invention disclosed herein, allelectrode' platesof the'v saule' polarity are given substantially thesame thickness by subjecting them, in thev next treatment step 9, to athickness sizing operation. In this sizing treatment, each properlyloaded. and'acti-y vated sheet formation which haslexcess'iv thick.-nness is placed while wetin a die'wheie it is jected to relatively highcompacting .pressure-such as 2500 to 5000 p. s. i. (pounds persduarefbi? bringing down or compacting all activated sheet formations orelectrode plates of excessive tliinli'-LV ness to substantially the sameunifor'mthicke'ss. This sizing treatment may be applied to' the sheet`formations before subjectiiig`A them el trolytic forming treatment by asuccessi charges and discharges ofr the Vtype d'escrib above. Y L I Ingeneral, the capacity of nickel-'cadmium batteries of the'-typedescribed above and' of' opposite polarity electrode plates ofsubstantially the same thickness-is limited by the capacity or theactive material of the positive electrode plates because a relativelylarger amount of the required negative electrode material is present ineach negative plate of such battery.

In accordance with the invention, the sintered nickel particle sheetformation, used for making nickel-cadmium battery plates of oppositepolarity in the manner described above, are sized for thickness and thegroup of thicker sheet formations are segregated from the group ofsomewhat thinner sheet formations produced by the sinteringv operation;`and the group or groups of the segregated thicker sheet formations areused for forming positive electrodes While the groups of segregatedthinner sheet formations are used for formingthe negative electrodes.After completing the activation of the groups of segregated `positivethicker sheet formations and of the groupsof segregated negative thinnersheet foi'- niatiorisfby the seriesof treatment steps describedabove'f-'each of the-two groups of sheet formations is subjectedV to asizing treatment wherebyV they are brought to substantially the sainethickness.- with thenega-tive battery plate formations being either ofthe-saine thickness, such as .025, oi'f slightly thinner than thepositive electrode sheet formations.

thenezst-treatment,l step 11, the washed and sized-sheet' formationsvvare stacked flat in superposed relation; under a flattening weight whichpresses-them flat, and they are then dried in this n conditionsSeparator' sheets,- of lter Ypaper and -'`plas'tic of -ma-terialsuch asApolystyrene are placed betweenadjacent sheet formations. The dryingiscarried on -at-temperatures such as C-. or less until they reachconstant weight.- f n this condition, they are ready to be cut intobattery plate sections for `assembly -into batteries.

the next treatment, step l2, the formed iiat A sheet formations are cutsubstantially along the center of their narrowY compacted separatingzonesSE-into the' separated individual electrode #sections-581 Eachelectrode section kd8 (Figs. 5

aifid;f8 '--'Alu-hasa--narrow' highly compacted thin edgereglo'n'bordering 4the relatively large body area of each plate section havingthe desired full thickness'and-with the pores thereof filled to thedesi-red extent withl the active positiver and negativeele'ctrodematerials, respectively, as described above;` y

linthe'i'iex'tjv 13ths'tep, the thin edges 55 of each separated platesection (Figs: 7, 8) are coated on -treati-id with a coating of cementmaterial whichbinds-any` loose particlesv of the edge formation of suchplate section and also provides an adherent'l insulating coatingenclosure around l any sharp; ends ofthe Wire mesh exposed by thewfcutting operation'. By this treatment, there are avoideduncontrollableand disturbing difficulties encountered-in the'past resulting inunpredictable-short circuits betweenopposite polarity electrede-plates'of the batteries formed of activated positive-and negative'electrodeplates, which dif- 'culties developed in v prior art sintered platenickel-cadmium batteries' usually inthe initial operation stages.

By providing each highly compacted cut edge region 55 of Veach electrodesheet section 5B with amentinous insulating coating enclosure, au looseparticles of such adge region are firmly bound place. In addition, allends and edges of Wires ofthe backing niesh 53 is likewise eilsfd" i" a"pte'c'tive enclosure which supaereas il presses any tendency of such cutwire ends from penetrating a separator formation separating the edgeregion of one electrode from the next adjacent electrode of oppositepolarity and thereby establish a short circuiting bridge therebetween.

Any alkali resistant cement or paint may be used for such edge coating,Among suitable coating materials are any of the known alkali resistantcoating compounds of styrene, styrenated oils, styrenated syntheticresins which are commercially available on the market. Also, aqueousdispersione of vinyl chloride Vinylidene chloride polymer, vinyl acetatepowder dispersed in glycols and polyglycols and Water, a polyethylenesolution in aromatic hydrocarbons, and like cementitious coatingmaterial.

Fig. 8-A shows in cross-section a compacted thin edge portion 55 of anelectrode plate 58 to which a thin coating layer 55-2 of suchcementitious coating material has been applied to the entire peripheryof such electrode plate 58. Fig. 8 shows a thick protective layer 55-1of alkali resistant plastic material applied or secured to the thincompacted edge portion 55 of such electrode plate 58 along its entireperiphery so that each electrode plate has along its compacted edgeregion 55substantially the same thickness as its main `electrode regionbounded thereby. The thick protective layer 55-1 may be formed ofsuitable alkali resistant plastic or resinous, nlm material, made in theform of a channel formation and secured to the thin edge region 55 ofthe electrode plate`58, either by a cement, isuch as cementitiouscoating compound of styrene, or the 1ike, or by heat sealingvtheprotective layer 55l to the underlying portionsof the edge region 55.Any alkali resistant thermoplastic film material may be used for Y theprotective .layer 55-I, such as polyethylene, polyvinyl chloride andsimilar thermoplastic material.-

In'the 'next 14th and last steaeach Velectrode plate section 58 isprovidedl with an electrode lead 66 (FiglS) formed of a stripnof nickelsheet material affixed, as by welding, to the compacted terminal portion59 ofthe electrode section 58 which has almost 100% density and permitsready and rm electric Welding of a nickel electrode tab 6B thereto.

In accordance with another' phas'e'f th infv vention, the largemulti-sectionfsheet formations 54, suchas vshown vin Fig, -afterdfullyloading, activating and sizing inthe manner described above, and beforecutting themlinto individual electrode plate sections584have applied, totheir compacted separation regions Eiland their edge regions l, anelec'tricallyinsulating plastic or resinous protective film formation*so as' to assure that when cutting the sheet formation' into sepa; rateelectrode sections 58 along their separation zones 55, the cut edges ofeach electrode sheet section 58 will be provided with anelectricallyinsulating coating enclosure for preventing loosening of any powderparticles thereof. 1n addition, after cutting, the edges of each soYpreviously coated sheet edge formation are further heated or coated toassure lthat allends of the wire mesh exposed along the edges by thecutting operation are covered by a 4iilm of resin or plastic materialadhering and united thereto for preventing development of a shortcircuiting bridge between adjacentopposite polarity electrodes of thebattery.

By the series of procedures such as described above, there are thusprepared sets of positive electrode plate sections 58 and setsofnegative 12 electrode plate sections 58, each section having anelectrode tab 65, suitable for assembling therefrom a batterysub-assembly such as shown at 38 in Figs. 1 to 3.

In such plate sub-assemblies, the alternate electrode plates 53 ofopposite polarity must be separated from each other in a reliable mannerby an insulating separator which permits substantially unimpededelectrolytic conduction through the liquid electrolyte placed betweenadjacent plates while suppressing the possibility of the development ofany formations which tend to form a short circuiting bridge betweenadjacent electrode plate portions of opposite polarity, or in general,preventing the possibility of any partial or full short circuit betweenthem.

According to a phase of the invention disclosed herein, an effectiveseparator for such battery electrode plates is provided by a continuousthin electrolysis pervious nlm with the film backed on its oppositesides with a fabric layer of alkali resistant threads or filaments.

Referring to Figs. 10 and 11, the battery assembly 38 has adjacentbattery electrode plates 53 of opposite polarity separated by adjacentsections l of a separator formation of the invention. The separatorformation l consists of a central film 12 backed on opposite sides by alayer of fabric '33. Suitable materials for the electrolysis perviousseparator nlm l2 are films of regenerated cellulose (cellophane) withoutplasticizer, and similar lrns of regenerated nitrocellulose and oforganic esters and ethers of cellulose Which may be partially saponied,such as cellulose acetate and ethyl cellulosek and also films of vinylalcohol polymer, all without plasticizer. Also, microporous films whichare resistant to alkali solutions and permit electrolytic action throughthe pores, such as films produced by forming a lm out rof polyvinylchloride dispersed and/or dissolved in a solvent and having adrnixedthereto dissolvable additions, such as starchror dextrin, and afterdriving off the solvent, the starch or dextrin additions thereof areremoved, for instance, by a treatment with sulfuric acid solution at to100 C. or by such sulfuric acid treatment preceded by a treatment with acaustic alkali.

Any of the known alkali resistant fibrous or ,iilamentary materials maybe used for the backing fabric layers '3 on the opposite sides of thecontinuous film layer E2 of the separator ll. Among suitable fiber orfilament materials for such backing fabric layers 73 are the nylons,polyethylene therephthalate (Daeron), acrylonitrile, polystyrene,vinylidene chloride, vinyl chloride, polyvinyl chloride and the like.

As seen in Figs. l and 2, the battery top or cover Wall l5 of thebattery cell is relatively rigid and is provided with a generallyrectangular border portion I6 arranged to fit within the interior of theadjoining end of the battery cell casing II-D. The intertting surfacesof the top wall I5 and cell casing walls H- are hermetically joined toveach other as by a suitable alkali resistant cement,'such ascementitious compounds of styrene, vstyrenated oils, styrenatedsynthetic resins 'whichV are commercially available on the market.Alternatively, the interitting walls may be affixed to each other byheat sealing. .Y

-The electrolyte within the interior-of the cell casing II-I ismaintained at a level of about 1A to l inch abovethe upper level of theelectrode .plates of the electrode assembly 30nposiasians* I3 tioned inthe inner part of the-batteryV cell casing ll-2.

In the form shown, the top wall of the battery casing has at its centera vent and lling opening I1. The top wall opening Il is shown closed bya closure member 8| of; alkaline resistant metal, to wit, nickel, havingat its lower Vend a threaded portion 82 arranged to threadedly engagethe threaded walls surface of the top wall opening Il. The closuremember 8| is shown provided with an intermediate sealing flange 83arranged toA overlie and clamp an underlying sealing washer 84, ofneoprene, for instance, b-y means of which the closure member seals olfthe top wall opening I'I when the closure member is in its sealingposition (Figs'' l, 1-A, 2). The outer end of the' closure member 8I isprovided with a head 85 having on its exterior aslit so that itsthreaded inner end 82 may be readily screwed in and out, as by a screwdriver, from its threaded engagement with the threaded top wall hole I1.

The outer vpart of the closure member 8| has an outer head 85 andvintermediate closure flange 83 which is enclosed With a tubular sealingsleeve member 86 of yieldable elastic rubber-like material.` The closuremember 8| is provided with a downwardly extendingaxial Vent passage orborel 81' having at its top aflateral outlet opening 88 which isnormally maintained sealed by the elastic pressure of the" sealingsleeve 88. The vent Apassage 8l and its sealing sleeve 86y are sodesigned that under excessive-gas pressure developed in theY interiorVof the sealed cell casing IIe-8, the gases will lift the sealing sleeve86 from the vent outlet opening 88 and permit gases to escapetherethrough. ,l Y

The top wall I5 is-provid'ed with an upwardly extending centraltubularwa-llnportion I8 of the top wall I5 surroundingY the outer part*of the closure member I8 and serving asa well or retainer structure forretaining electrolyte discharged through the VentopenngpaSSage 81, 88with the gases expelled therethrough.

The ventopen'i-ng region H5 of they top wall I5 is also provided with aninwardly extending tubular spray baille structure I9 for suppressingspraying of electrolyte into the top wall opening I'! by gases evolvedduring the charging operation. In the'form shown, the tubular spraybaille IS terminates at its lower end slightly above the upper edge ofthe battery plate assembly. 30 and serves l as a stop against outwardmovement of the battery assembly when it is accelerated by impact forcesfrom its inward position towards the top wall i5.

Batteries of the type described above are characterized by very highdischarge capacity under short circuit conditions and will operateduring a very long, useful life under a variety of adverse conditionswhich would impair the operation of other batteries. By way of example,and without thereby limiting the scope of the invention, there are givenin Figs. ll-A, 11-B. and ll-C, curves showing typical dischargecharacteristics of one form of a battery based on the principles of theinvention. The specific battery had 8 positive electrode plates and 7negative electrode plates each plate being 1 inch wide, 21A inches longand .025 inch thick. Fig. 11-A shows the discharge conditions of suchbattery cell for a constant current discharge of amperes, the dischargeconditions during the iirst ten seconds being shown on an enlarged scalein an auxiliary curve portion to the right of Fig. 1-1. Fig'. 11e-Bfand4 .r1-0' show'cone-f sponding discharge characteristics fordischargesl with a constant current at-the rate of 38 ain-- peres and50V amperes, respectively'.

The present application is directedto electrode plates of alkalineelectricstorage batteries lcom prising a porous plate of sintered nickelpowder particles reinforced by a backing layer, the plate beingcompacted along its edge regionsl and having a coating of electricallyinsulating material affixed and enveloping the thin edge regions of the`electrode plate. Other features of invention disclosed in thepresentapplication but not claimed therein are the subject matter' ofthe copending applications, Serial Nos. 277,841, 277,842, 277,843 and'277,844 filed March 21, 41952.

The features and principles' underlying the invention described above inconnection with specific exemplifications will suggest to those skilledin the art many other modifications thereof. It is accordingly desiredthat the appended claims shall not be limited to anyY specic features ordetails shown and described in connection with the exempliiicationsthereof I claim: ,Y

1. In an electric storagebattery cell of the alkaline type havingraplurality of alternately arranged positive'and negatieve electro-deplates', each plate constituting a thin Asheet structure comprising alayer of sinterednickel powder par@ ticles of substantialV porosityhaving united'A thereto a thin backing layer o f continuous'- metalelements extending in a direction of at least one major dimension ofsaid `s hjeet structurethe powder particles along, the edges of saidsheet structure being compacted againstvsaid backingl layer to providethin edgeregions of a thickness at most about half the` thickness of themajor area of said sheet structure and freenof any continuous metalelementsQpother thansaid backing layer, and a. coating of electricallyinsulating material aixed to and enveloping theL thin edge region ofsaid electrode plate throughout substantially the entire peripherythereof.v l

2. In an electric storage battery cell of the alkaline type having aplurality of alternately arranged positive and negative electrodeplates, each plate constituting, a thin sheet structure' comprising alayer of sintered nickel powder particles of substantial porosity havingunited thereto a thin backing layer of continuous metal elementsextending in a direction of at least one, major dimension of said sheetvstructure, the powder particles along the edges of said sheet structurebeing compacted against said backing layer to provide thin edge regionsof a thickness at most about half the thickness of the major area ofsaid sheet structure and free of any continuous metal elements otherthan said backing layer, and a coating of electrically insulatingmaterial ailxed to and enveloping the thin edge region of said electrodeplate throughout substantially the entire periphery thereof, theportions of said insulating coating overlying the side areas of saidedge region being of a thickness which gives said edge regionsubstantially the same thickness as the major area of said plate boundedby said edge region.

3. In an electric storage battery cell of the alkaline type having aplurality of alternately arranged positive and negative electrode platesand thin electrolyte pervious insulating separators separating saidplates and including a fastening sheet formation wound around theassembly of said plates for joining said plates into a self-supportingelectrode assembly, each plate constituting a thin sheet structurecomprising a layer of srintered nickel powder particles of substantialporosity having vunited thereto a thin backing layer of continuous metalelements extending in a direction of at least one majordimension of saidsheet structure, the powder particles along the edges of saidAsheetstructure being compacted against said backing layerr'to providethin edge regions of a thickness at most about half the thickness of themajor area of said sheet structure and freerof any continuous metalelements other than said backing layer and a coating of electricallyinsulating material afixed to and enveloping the thin edge region ofsaid electrode plate throughout substantiall the entire peripherythereof. Y

4. In an electric storage battery cell of the alkaline type having aplurality Aof alternately arranged positive and negative electrodeplates and thin electrolyte pervious insulating separators separatingsaid plates and including a fastening sheet formation Wound around theassembly of saidplates for joining said plates into a self-v supportingelectrode assembly, each plate constituting a thin sheet structurecomprisinga layer of sintered nickel powder particles of substantialporosity having united thereto a thin backing layer of continuous metalelements extending in a direction of at least one major dimension ofsaid sheet structure, the powder par# ticles along the edges of saidsheet structure being compacted against said backing layer to providethin edge regions of a thickness at most about half the thickness of themajor area of said sheet structure and free of any continuous metalelements other than said backing layer and acoating of electricallyinsulating material aixed to and enveloping the thin edge region of saidelectrode plate throughout substantially the entire periphery thereof,the portions of said insulating coating overlying the side areas of saidedge region being of a thickness which gives said edge regionsubstantially the same thickness as the major area of said plate boundedby said edge region.

5. In the process of producing electrode plates for alkaline storagebattery cells out of selfsuppcrting sheet formations, each comprising aporous layer oi' sintered nickel powder particles and providing suchsheet formation having an area which is Aat least several times greaterthan thevarea of the desired electrode plates, compact- 16 ingsaid sheetformation along narrow separation Zones of low porosity and a thicknessofat most half the thickness thereof which separates said sheetformations into several sheet sections of areas corresponding to theareas of several desired electrode plates, subjecting the integral sheetformation to treatments wherein the pores of the several sheet sectionsare loaded with desired active electrode material which is modiiicd whencharging or discharging a cell, and prior to cutting said sheetformation, ainxing to the opposite sides of the compacted zones of saidsheet formation Va coating of electrically insulating material. Y

6. In an electric storage battery cell as claimed in claim l, the poresof each of said plates being loaded with active electrode material whichis modified when discharging and charging said battery cells, thepositive plates containing difierent active electrode material than thenegative plates.

7. In an electric storage battery cell as claimed in claim 2, the poresof each of said plates being loaded with active electrode material whichis modied whenv discharging and charging said battery cells, thepositive plates containing different active electrode material than thenegative plates. 4 A

8. In an electric storage battery cell as claimed in claim 3, the poresofeach of said plates being loaded with active electrode materialwhichis modiiied when discharging and charging said battery cells, thepositive plates containing dierent active electrode material thanthenegative plates. Y

9. In an electric storage battery cell as claimedA in claim 4, the poresof each of said plates being loaded with active electrode material whichis modified when discharging and charging said battery cells, thepositive plates containing different active electrode material than thenegative plates.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Y 1,940,385 Ackermann Dec. 19, 1933 2,254,286 Hauel Sept. 2,1941 2,361,378 Brennan Oct. 31, 1944 2,366,402 Hauel Jan. 2, 19452,544,112 Schneider Mar. 6, 1951 2,561,943 Moulton et al July 24, 1951

